الفهرس 
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Abstract
The current in-vitro study was carried out to evaluate the bond strength of glass fiber dowels to root canal dentin using 3 different cementation techniques. Thirty freshly extracted human periodontally involved single rooted lower premolars were selected. The external surfaces of anatomically similar roots of selected teeth with fully developed apices were cleaned from soft tissue and calculus using hand scaler. Crowns of selected teeth were removed using a low speed diamond saw, under water cooling, leaving a root segment with 15±1 mm length. Roots were embedded in self-cure acrylic resin blocks. A step-back technique was used for the shaping process and 17% EDTA as the final rinse. Specimens were obturated with gutta-percha cones and resin-based endodontic sealer using a lateral condensation technique. Gutta-percha was removed using gates glidden. Dowel space was completed for each root canal with special preparation drills supplied from the dowel manufacturer using a low speed hand piece, leaving 4-5 mm apical seal. The dowel space was prepared to depth of 10-mm from the coronal surface corresponding to 1.3 mm DentoClic glass fiber dowel size 3. Following dowel space preparation, each root canal was irrigated with sterile water and dried with paper points. A radiograph was taken to evaluate the presence of any residual gutta-percha on the walls of the canals Specimens were divided randomly into 3 groups (n=10) according to the cement used for the fiber dowels into: total-etch (Variolink N - NX3); self-etch (Panavia F 2.0 - Duo-Link ™); and self-adhesive system (G-Cem – Calibra). Five doweled roots per group were destined to thin-slice push-out bond strength testing. Each root was sectioned into five or six 1-mm-thick slices under water cooling using the Isomet saw. The level of the dowel space from which each slice was derived was noted in order to discriminate among the retentive conditions provided by the luting agents at the coronal, middle and apical thirds of the dowel space. The loading force was extended in the apical-coronal direction in order to move the dowel toward the larger part of the root slice with a crosshead speed 1 mm/min plunger attached to a universal testing machine until failure occur. The latter was manifested by the extrusion of the dowel segment from the root slice. The level of the dowel space from which each slice which derived was noted in order to discriminate among the retentive conditions provided by the luting agents at the coronal, middle and apical thirds of the dowel space. Results showed that total-etch Variolink N cement had higher mean bond strength (15.36 ±3.15 MPa), and the lower mean bond strength (7.40±1.84 MPa) were found for self-adhesive Calibra cement with all the three regions of the root canal. Regardless of the cement used, coronal region of the root canal had the highest bond strength, and the apical region had the lowest bond strength. However, results of the middle region was intermediate.